Abstract

In recent decades, Escherichia coli 0157 and Salmonella spp. haveemerged as important human pathogens. They both cause a broad range of human illnesses that have the potential to be very harmful to the infected individuals, causing gastroenteritis, bloody diarrhoea and haemolytic uremic syndrome. This study proposes reasons for why there are differences in the outbreaks of E. coli 0157:H7 in England, Wales & Scotland, and if the high incidence of Salmonella spp. can also be caused by the same risk factors. The routes of transmission have changed over time, with new routes of transmission such as farm visits emerging. The prevalence of E. coli 0157:H7 and Salmonella spp. are seasonally dependent with greater faecal shedding of the organism in the warmer months; this is directly mirrored to the increased reporting of these bacterial infections among hospitalized patients. This thesis attempts to suggest why this phenomenon occurs, paying particular attention to weather, animal movement and private water supplies. This thesis has shown that cattle densities and human infection are occurring in similar regions and that temperature, sunshine and infection rates show a strong correlation in England & Wales. There is a statistically significant correlation between E. coli 0157:H7 & Salmonella spp. infection and sunshine, and slightly less so between infection and temperature. When comparing the mean sunshine and E. 'COli 0157:H7 data, a strong correlation was seen at lag -1 & -2 months, mean temperature data also showed a similar correlation at O & -1 months. A 'similar pattern was seen for the mean sunshine and Salmonella spp. data, with a pattern at -2 months. Temperature and Salmonella spp. infections also showed a significant correlation at -1 months. This lag period suggest that there is a time lag between the weather and acquisition of infection, which may be a cause in the incidence of E. coli 9157:H7 and Salmonella spp. it is interesting to speculate that cattle faeces which survives in a field may cause infection one or two months after, coinciding with the time lag period. It is suggested that further and more detailed studies are required to strengthen the hypothesis.